Here's Elon Musk's plan to create a 'self-sustaining' city on Mars 06-15

He says, his only motivation for accumulating personal wealth is to make human inhabitation interplanetary.Humanity will go extinct unless it reaches for the stars and colonizes a new planet.

That's what Elon Musk says, at least. The tech billionaire wrote a new paper detailing his vision for a "self-sustaining city" on Mars that was published in the scientific journal New Space earlier this month and posted online Wednesday.

The 16-page commentary details ideas the SpaceX CEO has been mulling over for years and most recently presented at the International Aeronautical Congress in Mexico last September. But his outline for the journey is now available in print, complete with accompanying charts and illustrations. Now, the scientific community will be able to scrutinize the proposal at its convenience.

Musk writes the paper in such a candid manner that he almost makes the roughly 140 million mile trip seem easy. " There really is a way that anyone could go if they wanted to," he says. The main obstacle, Musk argues, is the high cost of transporting people to the red planet. Using traditional methods like the approach that was used to send men to the moon in 1969, he estimates that it would cost about $10 billion per ticket. Musk has a much more feasible target in mind.

"If we can get the cost of moving to Mars to be roughly equivalent to a median house price in the United States, which is around $200,000, then I think the probability of establishing a self-sustaining civilization is very high," Musk writes. "I think it would almost certainly occur."

In order to achieve that price point, Musk outlines several steps to improve the cost of Mars travel by "five million percent": Spaceships must be fully reusable, they should be able to refuel in orbit, and then once again on Mars with fuel that is yielded from production plants built on the planet. Musk states that methane is the ideal propellant because the technical challenges to harvest it on Mars are significantly easier than substances like hydrogen, which he says is too expensive.

Once the engineering demands are met, it would be time to take off — which Musk is hopeful could begin as soon as 2023, according to an illustration in the paper. At least one million people would be needed to establish a self-sustaining city, he writes, estimating that spacecraft would be able to accommodate 100 people every two years. At that rate, he says it'll take "40-100 years to achieve a fully self-sustaining civilization on Mars."

A table in Musk's paper shows estimates that ships departing from Earth will take an average of 115 days to get to Mars once initial test flights begin in 2020. And the trip will be highly entertaining, according to the business mogul.

"... It has got to be really fun and exciting — it cannot feel cramped or boring," Musk writes. "Therefore, the crew compartment or the occupant compartment is set up so that you can do zero-gravity games — you can float around. There will be movies, lecture halls, cabins, and a restaurant. It will be really fun to go. You are going to have a great time!"

Musk says that ultimately the undertaking will be an enormous public private partnership funded between SpaceX, the private sector and the government.

"NASA applauds all those who want to take the next giant leap – and advance human exploration in deep space. We are very pleased that the global community is working to meet the challenges of a sustainable human presence on Mars," the space agency said in a statement to Fortune. "This journey will require the best and the brightest minds from government and industry, and the fact that Mars is a major topic of discussion is very encouraging."

And why should mankind look towards Mars instead of, say, the Moon, according to Musk?

"I think it is challenging to become multi-planetary on the moon because it is much smaller than a planet," he writes. "It does not have any atmosphere. It is not as resource-rich as Mars. It has got a 28-day day, whereas the Mars day is 24.5 hours.

"In general, Mars is far better-suited ultimately to scale up to be a self-sustaining civilization," Musk says.